The development of a light emitting device capable of emitting light with high brightness has shown significant progress in recent years.
The following kinds of light emitting devices are available.
An LED and an LD emit light by injecting an electron and a hole into a semiconductor pn junction formed of a high-quality crystal and recombining the electron and the hole.
An inorganic EL causes electrical field excited light emission by applying a high electric field to an insulating phosphor thin film and exciting a light emitting center in the phosphor thin film with hot electrons.
An organic EL is obtained by laminating a light emitting layer, an electron transporting layer, and a hole transporting layer formed of an organic molecule or a polymer thin film. The organic EL causes exciton light emission localized in an organic molecule with the energy of recombination between an injected electron and an injected hole.
An LED and an organic EL capable of emitting light with high brightness through a direct current drive are each requested to not only have higher brightness but also be developed to be more simple with excellent productivity and high durability.
Japanese Journal of Applied Physics 31, L 1606, 1992 discloses a DC drive type light emitting device using a chalcopyrite semiconductor, the light emitting device being of an MIS type diode constitution formed of Al/ZnS/CuGaS2. In this light emitting device, an electron is injected through a Schottky barrier between a metal layer and an insulating layer, whereby green light having weak intensity is emitted in a semiconductor layer.
In addition, Journal of Physics and Chemistry of Solids 66, 1868, 2005 discloses a constitution in which a heterojunction diode obtained by laminating a p-type CuGaS2 chalcopyrite semiconductor layer and an n-type ZnO:Al compound semiconductor layer is sandwiched between metals different from each other in work function. Attempts have been made to produce a DC drive type light emitting device having this constitution. At present, however, only light having weak intensity can be emitted from such device.